I just inspected the file acs-kernel/sql/postgresql/postgres.sql and it looks like the "iscachable" functions defined there will work fine with the new definition.  If you think I've missed some that won't, post here and I'll take another look.

The function in file-storage which gets the root folder for a given package will FAIL under the new definition.  It should be defined "stable".  In practice since it is rarely, if ever, called more than once per query we should probably not cache it in PG at all.  If caching it makes sense - and it's a cheap function so it may not really matter - let's do it at the Tcl level.

Similar things can be said about the proc that returns the package_id associated with a particular root folder.

Hmmm...simplest would be to just remove the "iscachable" altogether from HEAD and 4.6.1 (if that will include the PG 7.3 patches) ... Jeff, what do you think?

These are the only uses I found in the openacs-4 tree.  All other "iscachable" references are to the similar concept that's implemented by the Service Contract package.